The present invention relates to a resin and a process for using the same in forming a photoresist pattern. In particular, the present invention relates to a resin for reducing or inhibiting the amount of light reflecting from the lower film layer of a wafer (i.e., semiconductor substrate).
During a photoresist pattern formation step in a semiconductor fabrication process, standing wave effect and reflective notching phenomenon occur due to variations in the optical properties and the thickness of a layer of film coated below the photoresist layer and the photoresist layer itself. In addition, a change in the critical dimension (CD) can occur due to diffracted and reflected light from the lower layer. Accordingly, a reflection-inhibiting film that is capable of absorbing the reflected light is often coated on to the substrate below the photoresist layer. The reflection-inhibiting film includes a material which has a high absorbance of the wavelength of light used in the photoresist pattern formation.
A reflection-inhibiting film can be generally classified as an xe2x80x9corganicxe2x80x9d film or an xe2x80x9cinorganicxe2x80x9d film according to the type of materials used. The reflection-inhibiting film can also be catagorized as an xe2x80x9cabsorption-typexe2x80x9d or an xe2x80x9cinterference-typexe2x80x9d film.
The process for forming a photoresist pattern using i-line (365 nm) radiation has typically used an inorganic reflection-inhibiting film. For example, TiN and amorphous carbon (a-C) are typically used for absorption-type reflection-inhibiting films and SiON is generally used as interference-type reflection-inhibiting films. In a photoresist pattern formation using KrF (248 nm) radiation, an inorganic reflection-inhibiting film, SiON, is typically used but an organic reflection-inhibiting film has also been used.
However, a suitable reflection-inhibiting film has not been developed for a photoresist pattern formation process using ArF (193 nm) radiation. To date, it is believed that an inorganic reflection-inhibiting film for controlling interference of a 193 nm wavelength (e.g., ArF light source) has not been disclosed. Currently, extensive efforts are directed to developing an organic substance that can be used as a reflection-inhibiting film.
The basic requirements for a conventional KrF organic reflection-inhibiting film are: first, the reflection-inhibiting film must not be dissolved or removed during the process by the solvent used in the photoresist composition. Therefore, the reflection-inhibiting film is designed to form a cross-linked structure without generating chemical substances.
Second, chemical substances, such as acids and bases (e.g., amines), must not migrate through the reflection-inhibiting film. When an acid migrates from the reflection-inhibiting film, a phenomenon known as xe2x80x9cundercuttingxe2x80x9d takes place at the lower portion of the pattern. When a base such as an amine migrates, it may cause a xe2x80x9cfootingxe2x80x9d phenomenon in the pattern.
Third, the reflection-inhibiting film must have higher etching speed than the photosensitive film above it so that the etching process can be performed smoothly using a photosensitive film as a mask.
Fourth, the reflection-inhibiting film must inhibit reflection with only a thin layer.
Accordingly, the present inventors have developed a resin for reflection-inhibiting film that satisfies all of the aforementioned requirements and can be used in a process for forming the photoresist pattern of a semiconductor device employing an ArF light source.
It is therefore an object of the present invention to provide a resin for reflection-inhibiting films (also referred to as a polymer) that can inhibit reflection from a lower layer during an ArF light source mediated photoresist pattern formation step in a semiconductor fabrication process.
In order to achieve the above-described object of the present invention, there is provided a novel polymer comprising a phenyl group with high absorbency of 193 nm wavelength light and an epoxy group that enables cross-linkages to be formed during a hard baking step after the resin is coated on to the semiconductor wafer.